Surface Stress and Surface Tension in Polymeric Networks.

Area of Science:

• Materials Science
• Polymer Physics
• Surface Science

Background:

• Controlling adhesion, friction, and lubrication of soft polymeric materials relies on understanding surface property changes during deformation.
• Polymeric networks and gels are crucial soft materials with applications in various fields.

Purpose of the Study:

• To investigate the dependence of surface stress on deformation in soft and rigid polymeric network films.
• To elucidate the transition in surface properties from polymer melt-like to elastic solid-like behavior under varying strains.

Main Methods:

• Utilized a combination of theoretical calculations and coarse-grained molecular dynamics simulations.
• Studied surface stress (γ) in polymeric network films across a range of deformation ratios (λ).

Main Results:

• Polymeric network films exhibit surface properties of both polymer melts and elastic solids depending on deformation.
• At small deformations (λ/λ_max), surface stress (γ) equals the zero-strain surface tension (γ₀), resembling polymer melts.
• At large deformations, surface stress increases significantly due to bond deformation, showing elastic solid behavior, with normalized stress γ(λ)/γ₀ being a universal function of λ/λ_max.

Conclusions:

• The deformation behavior of polymeric network films dictates their surface properties.
• Bond deformation at high strains is the primary driver for the transition to elastic solid-like surface stress.
• Findings are crucial for tailoring surface properties of polymeric materials for specific applications.